Communication network probing is a technique increasingly used to monitor and analyze network traffic and transmission paths. The resulting insights are typically exploited by network operators for network management and optimization. As an example, network probing permits to identify possible bottlenecks within a communication network.
Network probing can be based on both live user traffic and dedicated probe (or test) traffic. For probe traffic generation specific test equipment, such as probe traffic generators, are installed at one or more network locations. The probe traffic generators are configured to initiate probe traffic communication with conventional network nodes, other probe traffic generators or special servers (such as reflectors). On the basis of the probe traffic, path properties such as packet loss, delay, jitter and throughput can be determined.
Network tunnels are transmission paths that require particular considerations when it comes to network probing. Generally, communication networks use tunneling protocols when a first network protocol (e.g., a delivery protocol) encapsulates a second network protocol (e.g., a payload protocol). As an example, the General Packet Radio Service (GPRS) Tunneling Protocol, also referred to as GTP, is a tunneling protocol used to transport in a GPRS core network user traffic between an access network and an external Packet Data Network (PDN) or another access network. The access network may be configured according to the Global System for Mobile Communication (GSM), Universal Mobile Telecommunications System (UMTS) or Long Term Evolution (LTE) specifications.
GTP is in fact a protocol suite that comprises multiple individual protocols, such as GTP-U and GTP-C. GTP-U is the user plane protocol applied to transport user data within the GPRS core network and between an access network and the core network. GTP-C, on the other hand, is the associated control plane protocol.
On the user plane, multiple tunnels may be set up for an individual user. Each tunnel is identified locally at a network endpoint by a Tunnel Endpoint Identifier (TEID). The TEIDs are randomly allocated by the tunnel endpoints. A Fully Qualified TEID (F-TEID) additionally contains address information (typically the Internet Protocol, or IP, address) of a given tunnel endpoint. Accordingly, a tunnel stretching between two endpoints can uniquely be identified by the F-TEID pair associated with the two end-points.
For network probing purposes, the GTP ECHO protocol permits to probe the connectivity between two devices supporting GTP. A network probing system on the basis of GTP ECHO messages is exemplarily described in WO 2008/138509 A.
It has been found that the end-to-end path from an access network via a core network to, for example, a PDN cannot yet be probed satisfactorily. This drawback can be attributed to the fact that tunnels specifically set up for probing purposes (“probe tunnels” hereinafter) do no route test traffic through certain network nodes that would need to be probed, such as Serving Gateways (S-Gws), Serving GPRS Support Nodes (SGSNs), PDN Gateways (P-Gws) and Gateway GPRS Support Nodes (GGSN). The same applies to network nodes above the P-Gw or GGSN (e.g., PDN servers on the Gi interface).
A further problem that has been observed is the fact that mobile communication systems often have two Transport Control Protocol (TCP)/IP layers. Most existing network probing solutions are only capable of probing the lower TCP/IP layer between two network nodes. This means that the upper TCP/IP layer that actually represents the end-to-end connectivity across the mobile communication system will not be probed.
To overcome this problem, mobile terminal-based probing solutions have been proposed to monitor the end-to-end connectivity. Such systems have the drawbacks that they consume precious radio resources and that they require additional hardware. As an alternative, an emulation of mobile terminals on the network side has been considered for end-to-end path probing. The emulation approach, however, necessitates the implementation of a complete mobile terminal stack and of user authentication mechanisms on the network side.
In sum, the presently available network probing approaches for tunnel-based transmission paths do not yet permit a satisfactory monitoring of an end-to-end connection and of individual network nodes in the core network. This drawback is based on the nature of the probe tunnels defining the transmission paths to be probed.